The human cardiovascular system serves as the material transport network in the body. It interfaces with the interstitial compartment via diffusion sites throughout the body and exchanges fluids, hormones, electrolytes, nutrients and other substances. This is achieved by the pumping function of the human heart and the blood circulation through blood vessels. The heart pumps the blood from the low-pressure venous system to the arterial side of the circulation under the proper pressure to maintain the circulatory needs of the body. The heart basically consists of four chambers: two thin-walled atria separated from each other by an interatrial septum, and two thick-walled ventricles separated by an interventricular septum. The heart is made up of two separate pump systems in series. The right atrium and ventricle act as a single unit to move venous blood from the great veins (superior vena cava (SVC) and the inferior vena cava (IVC)) to the pulmonary circulation where the venous blood becomes oxygenated by passing through the human lungs. The left atrium and ventricle act together to pump the blood from the pulmonary veins to the high-pressure systemic circulation. The blood circulates through the body and returns to the right atrium from the SVC and the IVC.
Heart failure happens when the heart cannot pump sufficient blood to meet the needs of body. Heart failure (HF) affects 5.7 million patients in the US, and it contributed to almost 280,000 deaths in 2008 (Roger et al. Circulation. 2012; 125(1):e2-220.). It creates a major burden on health care providers and is expensive to treat. The estimated direct and indirect cost of HF in the United States for 2010 was $39.2 billion (2010 Heart Failure Fact Sheet from Centers for Disease Control and Prevention). Despite the advances in medical care, prognosis with HF remains poor, especially in the advanced stages. Patients with advanced HF require mechanical circulatory assistance or heart transplantation to survive. Heart transplantation is limited by the supply of donor organs. Mechanical circulatory assistance is often achieved by using ventricular assist devices (VADs), which are mechanical pumps designed to augment or replace the function of one or more chambers of the failing heart. The use of VAD, though increasing, has been limited due to the need for major operative intervention.
Further, lung disease is the #3 killer in the United States, responsible for 1 in 6 deaths (American Lung Association). Annually 400,000 deaths are attributed to pulmonary causes in spite of $154 billion in expenditure (Sanovas. “Lung Disease”.). Lung failure occurs acutely or chronically. Chronic obstructive pulmonary disease (COPD) is one of the most common lung diseases and the 4th leading cause of death in the U.S. Adult Respiratory Distress Syndrome (ARDS) is commonly afflicting 190,000 patients yearly and the average survival rate is between 30-50% (Rubenfeld et al. N Engl J Med 2005; 353:1685-93,). If lung failure occurs, either mechanical ventilation or extracorporeal membrane oxygenation (ECMO) must be implemented to oxygenate the blood to maintain the need of the body for oxygen. Mechanical ventilation is effective for short-term support, yet the sustained tidal volumes and airway pressures often used may damage the lungs. The ECMO closely simulates physiological gas exchange, but requires cannulation to access the blood.
In current clinical practices, the use of VAD and ECMO both require major invasive surgical procedures to implant these devices via a set of cannulae. Thus, only a limited population of patients receives these device-based therapies. A cannula is a medical tube inserted into the body for drainage and infusion of blood. The major problems of the available cannulae for ECMO are (U.S. Pat. No. 7,473,239 B2 to Wang et al.): 1) multiple cannulation needs and insertion of cannulae with larger diameters cause extra trauma to patients; 2) when blood is drawn and reinfused from the right atrium or central veins, blood recirculation leads to insufficient extracorporeal oxygenation; 3) the placement of the drainage lumen against the vein causes insufficient venous blood drainage; and 4) direct cannulation of the heart can result in hemorrhage from fixating surgical sutures. Similarly, the currently available cannulae for VADs also have a similar problem of extra trauma. Therefore, a minimally invasive, efficient and simple percutaneous cannula system is needed for ECMO and VAD.